Position detection apparatus, position detection method, exposure apparatus, device manufacturing method, and substrate

ABSTRACT

A position detection apparatus which detects a position of a mark included in an object is disclosed. The apparatus comprises a sensing unit for sensing an image of the object, wherein a plurality of marks included in the object can be included in the image, a extracting unit for extracting feature of a region, other than a region of a target mark of the plurality of marks, of the image sensed by said sensing unit, and a calculating unit for calculating a position of the target mark based on the feature extracted by the extracting unit.

FIELD OF THE INVENTION

[0001] The present invention relates to a position detection apparatusand position detection method, an exposure apparatus, a devicemanufacturing method, and a substrate and, more particularly, to aposition detection apparatus and position detection method which detectthe position of a mark on an object, an exposure apparatus including theapparatus, a device manufacturing method using the apparatus, and asubstrate adapted to such a position detection apparatus.

BACKGROUND OF THE INVENTION

[0002] A semiconductor device is manufactured by repeating a lithographystep for projecting and exposing a device pattern formed on a master(e.g., a reticle or mask) to a substrate (e.g., a wafer or glasssubstrate) coated with a photosensitive material and developing thedevice pattern. In such a manufacturing step, it is important toaccurately align a device pattern (latent image) to be projected andexposed to a photosensitive material to a device pattern (patternedstructure) already formed on a substrate.

[0003] An example of operation for aligning the pattern of a master to apattern formed on a substrate is substrate alignment. In themanufacturing step of forming a semiconductor device on a wafer, suchsubstrate alignment is called wafer alignment.

[0004] Wafer alignment is performed in accordance with the followingprocedure. First, a wafer is supplied to a lithography system having anexposure apparatus and mechanical alignment apparatus. Coarse alignmentis done by the mechanical alignment apparatus using an orientation flator notch formed at the peripheral portion of the wafer. Then, the waferis placed on the wafer chuck of the exposure apparatus by a wafer supplyapparatus. The typical alignment accuracy by the mechanical alignmentapparatus is about 20 μm.

[0005] Next, the positions of a plurality of alignment marks (positiondetection marks) formed on the wafer by a preceding step are detectedusing an alignment scope. The X- and Y-direction shifts and rotationcomponent of the wafer and the magnification component of the shot arrayare calculated on the basis of the detection result. In exposing eachshot, the wafer stage is driven on the basis of the calculation result.Accordingly, the pattern already formed in a shot is accurately alignedto the pattern projected onto the wafer through a projecting opticalsystem. This scheme will be called global alignment. The accuracy ofglobal alignment is 50 nm or less in an exposure apparatus formanufacturing, e.g., a 256-Mbit memory.

[0006] In recent years, a planarization technique by a polishing stepcalled CMP (Chemical Mechanical Polishing) is often used. When CMP isexecuted, the layer on the alignment mark is polished. This degrades amark signal or decreases stability. To prevent this, an alignment markis often optimized in accordance with the process. This optimization isperformed by forming a plurality of tentative alignment marks havingdifferent structures such as line widths, pitches, and three-dimensionalpatterns and selecting an optimum alignment mark. Normally, an optimumalignment mark is determined at the time of prototype formation. In aflexible manufacturing system, however, mass production sometimes startswithout executing optimization. In this case, a plurality of alignmentmarks may enter the visual field of the alignment scope.

[0007] Additionally, in recent years, a method of forming a plurality ofsets of alignment marks in one region (exposure region) is replacing amethod of forming a set of X and Y alignment marks in one region. Thisaims at, e.g., correcting a deformation of the exposure region orincreasing the measurement accuracy by an averaging effect obtained bymeasuring a plurality of alignment marks. For such purposes, theaccuracy must be increased by ensuring the span between the alignmentmarks as wide as possible. More specifically, four alignment marks areformed at the four corners of each exposure region. Also with thisbackground, a plurality of alignment marks may enter the visual field(the field of view) of an alignment scope at a high probability.

[0008] Furthermore, as the number of steps increases recently along withan increase in complexity of device structure, the number of times ofalignment mark formation increases.

[0009] More specifically, the number or layout density of alignmentmarks increases in recent years in accordance with various purposes orfactors such as optimization of the alignment mark structure,improvement of measurement accuracy, and the increase in number ofsteps. Accordingly, a plurality of alignment marks enter the visualfield of an alignment scope. For this reason, the necessity foridentifying or specifying a target alignment mark from a plurality ofalignment marks in the visual field is increasing.

SUMMARY OF THE INVENTION

[0010] The present invention has been made in consideration of the abovesituation, and has as its object to obtain a position of a target markfrom an image of an object including a plurality of marks.

[0011] According to the first aspect of the present invention, there isprovided an apparatus which detects a position of a mark included in anobject. The apparatus comprises a unit which senses an image of theobject, wherein a plurality of marks included in the object can beincluded in the image, a unit which extracts feature of a region, otherthan a region of a target mark of the plurality of marks, of the imagesensed by the sensing unit, and a unit which calculates a position ofthe target mark based on the feature extracted by the extracting unit.

[0012] In the preferred embodiment of the present invention, the featuremay correspond to an auxiliary mark, included in the object, associatedwith one of the plurality of marks. The auxiliary mark can be connectedto one of the plurality of marks. The auxiliary mark can be associatedwith the target mark or one of the plurality of marks other than thetarget mark.

[0013] In the preferred embodiment, the feature may correspond torelative positions of some of the plurality of marks or a position ofone of the plurality of marks, of which a position relative to thetarget mark is known.

[0014] In the preferred embodiment, the object may include a substrateon which a device is to be formed.

[0015] In the preferred embodiment, the apparatus can further comprise astage unit which positions the substrate. In such an application, theapparatus can further comprise a unit which controls positioning of thesubstrate by the stage unit based on the position of the target markcalculated by the calculating unit.

[0016] According to the second aspect of the present invention, there isprovided an apparatus which exposes a substrate to radiant energy. Theapparatus comprises a stage unit which positions the substrate, a unitwhich senses an image of the substrate, wherein a plurality of marksincluded in the substrate can be included in the image, a unit whichextracts feature of a region, other than a region of a target mark ofthe plurality of marks, of the image sensed by the sensing unit, a unitwhich calculates a position of the target mark based on the featureextracted by the extracting unit, and a unit which controls positioningof the substrate by the stage unit based on the position of the targetmark calculated by the calculating unit.

[0017] According to the third aspect of the present invention, there isprovided an apparatus which exposes a substrate to radiant energy. Theapparatus comprises a unit which projects a pattern of radiant energy tothe substrate, a unit which holds a mask having an auxiliary pattern, tobe projected by the projecting unit, for identifying a target markformed on the substrate, and a unit which controls an operation ofprojecting the auxiliary pattern by the projecting unit.

[0018] According to the fourth aspect of the present invention, there isprovided a substrate comprising a region for a chip and a plurality ofmarks formed such that a position of a target mark of the plurality ofmarks is recognized.

[0019] According to the fifth aspect of the present invention, there isprovided a method of detecting a position of a mark included in anobject. The method comprises steps of sensing an image of the object,wherein a plurality of marks included in the object can be included inthe image, extracting feature of a region, other than a region of atarget mark of the plurality of marks, of the image sensed in thesensing step, and calculating a position of the target mark based on thefeature extracted in the extracting step.

[0020] According to the sixth aspect of the present invention, there isprovided a method of manufacturing a device, the method comprising stepsof sensing an image of a substrate, wherein a plurality of marksincluded in the substrate can be included in the image, extractingfeature of a region, other than a region of a target mark of theplurality of marks, of the image sensed in the sensing step, calculatinga position of the target mark based on the feature extracted in theextracting step, and transferring a pattern concerning the device to thesubstrate based on the position of the target mark calculated in thecalculating step.

[0021] Other features and advantages of the present invention will beapparent from the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

[0023]FIG. 1 is a view schematically showing the arrangement of alithography system (exposure apparatus) according to a preferredembodiment of the present invention;

[0024]FIG. 2A is a view showing an example of a group of alignment marksobserved in a low-magnification visual field;

[0025]FIG. 2B is a view for explaining auxiliary patterns used toidentify a target alignment mark;

[0026]FIG. 2C is a view showing an example of auxiliary patterns;

[0027]FIG. 2D is a view showing another example of auxiliary patterns;

[0028]FIG. 2E is a view showing still another example of auxiliarypatterns;

[0029]FIG. 3A is a view showing an example of a group of alignment markspartially observed in a low-magnification visual field;

[0030]FIG. 3B is a view for explaining change of a search range;

[0031]FIG. 3C is a view showing an example of layout of alignment marks;

[0032]FIG. 3D is a view showing another example of layout of alignmentmarks;

[0033]FIG. 3E is a view showing an example of a group of alignment markspartially observed in a low-magnification visual field;

[0034]FIG. 4 is a view showing a shot region and global alignment markson a wafer;

[0035]FIG. 5A is a view schematically showing the arrangement of alithography system (exposure apparatus) according to another preferredembodiment of the present invention, which has an auxiliary patterntransfer function;

[0036]FIG. 5B is a view for explaining the auxiliary pattern transferfunction;

[0037]FIG. 5C is a view for explaining the auxiliary pattern transferfunction;

[0038]FIG. 6 is a flow chart for explaining the procedure of globalalignment in the lithography system or exposure apparatus according tothe preferred embodiment of the present invention;

[0039]FIG. 7 is a flow chart for explaining the procedure of globalalignment in the lithography system or exposure apparatus according tothe preferred embodiment of the present invention;

[0040]FIG. 8A is a view showing an arrangement example of an alignmentmark;

[0041]FIG. 8B is a view schematically showing a situation in which analignment mark is moved into the visual field of a high-magnificationsensor;

[0042]FIG. 8C is a view showing a group of alignment marks in the visualfield of a low-magnification sensor;

[0043]FIG. 9 is a flow chart showing the flow of the entiremanufacturing process of a semiconductor device; and

[0044]FIG. 10 is a flow chart showing the flow of the entiremanufacturing process of a semiconductor device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] Preferred embodiments of the present invention will be describedbelow with reference to the accompanying drawings.

[0046] [First Embodiment]

[0047] An example of an alignment mark (position detection mark) to beused in global alignment in a lithography system or exposure apparatusaccording to a preferred embodiment of the present invention will bedescribed first with reference to FIG. 8A. An alignment mark FXY of thisembodiment is designed to make it possible to simultaneously executemeasurement in the X direction and that in the Y direction in globalalignment.

[0048] In global alignment, a mark FX for X-direction measurement in awindow X shown in FIG. 8A is observed with a high-magnification scope(high-magnification detection system or high-magnification observationsystem). Simultaneously, a mark FY for Y-direction measurement in awindow Y is observed with a high-magnification scope. With thisoperation, the X- and Y-direction positions (coordinates) of thealignment mark FXY are detected at a high resolution.

[0049] Global alignment according to the preferred embodiment of thepresent invention will be described next with reference to FIGS. 1 and4. When a wafer is supplied to a lithography system shown in FIG. 1 by atransfer mechanism (not shown), a mechanical alignment apparatus MAdetermines the coarse position of the wafer on the basis of theperipheral position of the wafer and the position of a directionspecifying portion (N in FIG. 4) called an orientation flat or notch.

[0050] Next, the wafer is placed on a chuck CH mounted on a wafer stageSTG by a wafer supply apparatus (not shown). After that, globalalignment is performed to accurately obtain the position of the wafer Wand the position of each exposure shot. In the global alignmentaccording to this embodiment, X-direction measurement marks FX1 to FX4and Y-direction measurement marks FY1 to FY4 in a plurality of globalalignment marks FXY1 to FXY4 on the wafer W are measured using ahigh-magnification scope (high-magnification detection system orhigh-magnification observation system), thereby obtaining the X- andY-direction shifts and rotation component of the wafer W from thereference position and the magnification component of the shot array.

[0051] An alignment scope which can observe the alignment mark FXY shownin FIG. 8A simultaneously with a low-magnification system andhigh-magnification system will be described next. A microscope for waferalignment, i.e., an alignment scope SC shown in FIG. 1 is designed tomake it possible to observe an alignment mark simultaneously with alow-magnification system and high-magnification system to detect theposition of the alignment mark.

[0052] Alignment mark illumination light is guided from an alignmentmark illumination light source Li into the scope SC, passes through ahalf mirror M1 (or a polarizing beam splitter), and illuminates analignment mark (e.g., the mark FXY1 shown in FIG. 4) on the wafer W.Reflected light from the wafer W passes through the half mirror M1 and ahalf mirror M2 and reaches a high-magnification detection sensor (e.g.,a photoelectric conversion element) S2. Simultaneously, the reflectedlight from the wafer W also passes through the half mirrors M1 and M2and reaches a low-magnification detection sensor (e.g., a photoelectricconversion element) S1. Images sensed by the sensors S1 and S2 aresupplied to a processing apparatus P. The processing apparatus Pexecutes a predetermined process to calculate the position of thealignment mark.

[0053] Calculation of the alignment mark position is done for each ofthe two sensors S1 and S2 of the low- and high-magnification systems. Anelectrical signal (image signal.) photoelectrically converted by thelow-magnification system detection sensor S1 is converted from an analogsignal into a digital signal by an A/D converter AD1 and then stored inan image memory MEM1 as image data. An arithmetic device COM1 searchesfor the alignment mark FXY (FX and FY) while executing a patternmatching process or the like for the image data in the image memoryMEM1.

[0054] A template for pattern matching can be constituted by atwo-dimensional pattern formed from, e.g., eight vertical lines andeight horizontal lines, as shown in FIG. 2B by example. The matchingprocess algorithm of template matching is designed such that not only amark that strictly has the same shape as that of the template but also amark whose line width or the like is different from that of a standardmark can be detected. More specifically, the mark detection algorithmallows detection of all marks even when a mark which has a shape similarto that of the template (shape with a common feature portion to bedetected), although its structure such as a line width or mark step isdifferent, is present in the image stored in the image memory MEM1,i.e., in the low-magnification visual field as well as marks having thesame shape as that of the template.

[0055] In addition, when two templates are prepared, marks that areclassified into two types, e.g., a mark having eight vertical lines andeight horizontal lines as shown in FIG. 2B as a characteristic featureand a mark (not shown) having six vertical lines and six horizontallines as a characteristic feature can be detected. Furthermore, when aplurality of templates are prepared, marks that are classified intotypes equal in number to the templates can be detected.

[0056] To detect alignment marks, various methods except templatematching and pattern matching can also be applied.

[0057] The reflected light for the high-magnification system can be madedifferent from that for the low-magnification system by using the commonillumination light source Li and adjusting the accumulation times in thesensors S1 and S2.

[0058] The principle of mark observation performed using thehigh-magnification system (M1, M2, and S2) and low-magnification system(M1 and S1) simultaneously will be described next with reference toFIGS. 8A and 8B. FIG. 8A illustrates an observable visual field HF ofthe high-magnification system (M1, M2, and S2). For both the X-directionpattern FX and the Y-direction pattern FY, shifts with respect to thewindows X and Y are hardly allowed.

[0059]FIG. 8B illustrates an observable visual field MF of thelow-magnification system (M1 and S1). The visual field MF of thelow-magnification system is wider than the visual field HF of thehigh-magnification system. The arithmetic device COM1 calculates smallmoving amounts dx and dy of the wafer W which should be moved to put analignment mark P1 to be detected into the visual field HF of thehigh-magnification system on the basis of the alignment mark observationresult (the position of the alignment mark to be detected) by thelow-magnification system (M1 and S1) while observing the alignment marksimultaneously with the high-magnification system and low-magnificationsystem.

[0060] High-speed wafer alignment using the alignment marks shown inFIGS. 2A and 2B and the alignment scope SC shown in FIG. 1 will bedescribed next as the preferred embodiment of the present invention. Thelight component that has passed through the half mirror M2 is guided tothe sensor S2 of the high-magnification system and forms the image ofthe alignment mark FXY on the image sensing surface of the sensor S2. Inaddition, the light component reflected by the half mirror M2 is guidedto the sensor S1 of the low-magnification system and forms the image ofthe alignment mark FXY on the image sensing surface of the photoelectricconversion element S1.

[0061] It is preferable to simultaneously form the images of thealignment mark FXY and simultaneously observe the alignment mark FXY.The reason for this will be described below. If the shift amounts dx anddy shown in FIG. 8B, which are obtained by the low-magnification system,fall within an allowable range, the image of the alignment mark FXY thatallows accurate position measurement is formed on the high-magnificationsystem sensor S2. Hence, the position detection result for the alignmentmark FXY using the high-magnification system sensor S2 is valid.

[0062] The allowable range means, in the example shown in FIG. 8A, shiftamounts with which it is determined that the pattern FX (pattern formedfrom eight lines) in the X direction and the pattern FY (pattern formedfrom eight lines) in the Y direction are present within the windows Xand Y, respectively. Hence, when the shift amounts dx and dy obtained bythe low-magnification system fall within the allowable range, anaccurate detection result (mark position) in the high-magnificationsystem can be obtained as quickly as possible. Conversely, when theshift amounts dx and dy obtained by the low-magnification system falloutside the allowable range, the stage STG is finely moved by dx and dy.After that, the mark position is detected again by thehigh-magnification system.

[0063] A mark identification method to be used when a plurality ofalignment marks having identical or similar shapes (shapes with a commonfeature portion to be detected) are present in the visual field MF ofthe low-magnification system will be described next with reference toFIG. 2A. A description will be made below assuming that the alignmentmark (i.e., the target alignment mark) to be detected in the currentlithography step (current exposure step) is P1.

[0064] When alignment was executed even in the preceding lithographystep before the current lithography step (e.g., when the currentexposure step is the exposure step of second or subsequent time), forexample, alignment marks L1, M1, M1, and O1 that were formed and used inthe preceding step and have the same shape as that of the alignment markP1 may be laid out adjacent to the current target alignment mark P1.Alternatively, the alignment marks L1, M1, M1, O1, and P1 may be markswhich have similar shapes (i.e., shapes with a common feature portion tobe detected) but different line widths and three-dimensional patternsfor the purpose of optimizing the alignment mark structure.

[0065] In this embodiment, to detect only the current target alignmentmark P1 from the visual field MF of the low-magnification system andobtain the shift amounts dx and dy (moving amounts for observation withthe high-magnification system), some or all of auxiliary patterns CPa,CPb, CPc, and CPd or no auxiliary patterns are added to regions that donot influence the measurement of the alignment mark FXY at a highmagnification, as shown in FIG. 2B, thereby identifying the targetalignment mark. For example, no auxiliary pattern is added to thealignment mark P1 while a small square is added to the upper rightportion of the alignment mark O1.

[0066] In this way, auxiliary patterns are added to regions that do notinfluence high-magnification measurement in the formation regions of thealignment marks L1, M1, M1, O1, and P1 to identify the alignment marksL1, M1, M1, O1, and P1. An auxiliary pattern is preferably formed in aregion outside a chip region where a device pattern (e.g., a circuitpattern) is formed and, typically, between chip regions.

[0067] The target alignment mark can also be identified on the basis ofthe positional relationship relative to a feature portion (e.g., aportion having an extractable feature) of a device pattern. In thiscase, however, a pattern that is much more complex than an alignmentmark must generally be detected as an auxiliary pattern, resulting in ahigh arithmetic process load.

[0068] In this case, the auxiliary pattern is inevitably part of thepattern of the device to be manufactured. Hence, the template to be usedto determine the target alignment mark depends on the pattern of eachdevice to be manufactured.

[0069] Furthermore, in this case, no auxiliary pattern can be determinedif, for example, device patterns around a group of alignment marks areuniform patterns having no feature portion or periodical patterns. Thatis, to use a pattern in a chip region as an auxiliary pattern is greatlyrestricted and is therefore undesirable.

[0070] Hence, as described above, an auxiliary pattern is preferablyformed on purpose (i.e., the auxiliary pattern is not inevitably formedas a pattern in a chip region but formed mainly for the purpose ofidentifying an alignment mark) in a region outside a chip region (i.e.,a region where formation of a mark or pattern for position detection isallowed).

[0071] A method of discriminating a plurality of alignment marks usingauxiliary patterns will be described next with reference to FIGS. 2A and2B. When alignment marks in the state as shown in FIG. 2A are present inthe visual field MF of low-magnification system (M1 and S1), thepositions of the five alignment marks are detected by the arithmeticdevice COM1 for the low magnification. A control apparatus MC determinesthe presence/absence of the auxiliary patterns CPa, CPb, CPc, and CPdshown in FIG. 2B for each of the five detected positions.

[0072] The presence/absence of an auxiliary pattern can be determined bya method of, e.g., executing template matching or analyzing a contrastchange using a histogram or the like for each of regions (in thisembodiment, the four corners of a rectangular region defined foralignment mark formation) where auxiliary patterns are to be formed.

[0073] The auxiliary patterns may be separated from a center C of thealignment mark equidistantly or by different distances. In the exampleshown in FIG. 2B, the center C is assumed to be the origin (referenceposition). The coordinates of the auxiliary pattern CPa are defined as(Xa,Ya). The coordinates of the auxiliary pattern CPb are defined as(−Xb,Yb). The coordinates of the auxiliary pattern CPc are defined as(Xc,−Yc). The coordinates of the auxiliary pattern CPd are defined as(−Xd,−Yd). Such pieces of coordinate information are loaded to theinternal memory of the control apparatus MC before the exposure process.

[0074] In this example, each auxiliary pattern is square. However, anauxiliary pattern need not always have the square shape and may haveanother shape (for example, a rectangle, circle, polygon, pattern,number, symbol, character, or the like may be used). As far as theauxiliary patterns can be observed in the visual field MF of the sensorS1, the distance between the alignment mark and each auxiliary patternis not particularly limited, i.e., they may be close to or apart fromeach other.

[0075] The control apparatus MC loads information shown in Table 1 belowto the internal memory (e.g., a RAM) as well as the coordinateinformation before the exposure process. The target alignment mark (P1in this example) can be discriminated on the basis of the information.TABLE 1 CPa CPb CPc CPd L1 present present absent absent M1 absentpresent absent absent N1 absent present present absent O1 present absentabsent absent P1 absent absent absent absent

[0076] To identify the target alignment mark P1, an alignment mark whosecombination of auxiliary patterns matches the combination assigned to P1in Table 1 is searched for from the five alignment marks. When thetarget alignment mark is discriminated on the basis of thepresence/absence of auxiliary patterns at the four portions, as in thisexample, the target alignment mark can be discriminated from 16alignment marks at maximum.

[0077] The procedure of global alignment in the lithography system orexposure apparatus according to the preferred embodiment of the presentinvention will be described next with reference to FIGS. 6 and 7. Theprocess shown in the flow charts in FIGS. 6 and 7 is controlled by thecontrol apparatus MC.

[0078] The schematic procedure of global alignment is indicated by stepsS101 to S107 in FIG. 6.

[0079] First, in step S101, the control apparatus MC outputs a commandto a stage control apparatus STC to cause it to move the wafer stage STGsuch that the alignment mark FXY1 shown in FIG. 4 enters the visualfield of the alignment scope SC. Typically, the stage control apparatusSTC moves the stage STG to the target position in consideration of theposition information of the stage STG, which is supplied from a stageposition measuring apparatus (e.g., a laser interferometer) LP.

[0080] Each of the alignment marks FXY1 to FXY4 shown in FIG. 4 isdesigned to have the pattern shown in FIG. 8A. As shown in FIG. 2A (notillustrated in FIG. 4), one or a plurality of alignment marks (L1, M1,M1, and O1 in FIG. 2A) whose feature portions to be detected are commonto those of the target alignment marks FXY1 to FXY4 (P1 in FIG. 2A) inthe current global alignment are present around the target alignmentmarks.

[0081] In step S102, the control apparatus MC outputs commands to theprocessing apparatus P, alignment scope SC, and illumination lightsource Li to cause them to detect the positions of the marks FX1 and FY1(i.e., the X- and Y-direction positions of the alignment mark) byobserving the marks FX1 and FY1 (corresponding to the marks FX and FY inFIG. 8A) of the alignment mark FXY1. The detection result is sent fromthe processing apparatus P to the control apparatus MC.

[0082] The process procedure in step S102 (and step S104 to be descriedlater) will now be described in detail with reference to the flow chartshown in FIG. 7. A description will be made here assuming that thehigh-magnification sensor S2 comprises an X-measurementhigh-magnification sensor for position measurement in the X directionand a Y-measurement high-magnification sensor for position measurementin the Y direction. In this case, each of the X-measurementhigh-magnification sensor and Y-measurement high-magnification sensorcan include, e.g., a line sensor. The high-magnification sensor S2 mayinclude an area sensor which simultaneously senses the mark FX1 (FX) forthe X-direction measurement and the mark FY1 (FY) for the Y-directionmeasurement.

[0083] In this embodiment, high-magnification image sensing of the markFX1 (FX) for the X-direction measurement (step S110) andhigh-magnification image sensing of the mark FY1 (FY) for theY-direction measurement (step S111) by the high-magnification sensor S2and low-magnification image sensing by the low-magnification sensor S1(S112) are simultaneously executed. These image sensing operations neednot always be executed simultaneously. However, when these operationsare executed simultaneously, the total process time can be shortened.

[0084] In addition, in this embodiment, position calculation of the markFX (step S113) and position calculation of the mark FY (step S114) atthe high magnification and position calculation of the target alignmentmark FXY1 (FX in FIG. 8A) and the remaining alignment marks andauxiliary patterns at the low magnification (step S115) are executed inparallel. The position calculation of the marks FX and FY at the highmagnification is executed by an arithmetic device COM2. The positioncalculation of the alignment mark FXY1 at the low magnification isexecuted by the arithmetic device COM1.

[0085] An image sensed at a high magnification may not include the imageof the target alignment mark FXY1. In this case, an erroneous position(coordinates) is calculated as the position of the target alignment markor the position calculation itself is impossible in steps S113 and S114.An example of the cause of such position detection error is misalignmentby the mechanical alignment apparatus MA. On the other hand, the visualfield MF of the low-magnification system is designed to allow such anerror. Hence, the target alignment mark can be sensed.

[0086] In step S115, the X- and Y-direction positions are calculated forall of the alignment marks L1, M1, N1, O1, and P1 (the target alignmentmark is P1) and auxiliary patterns CPa, CPb, CPc, and CPd in the visualfield MF of the low-magnification system (M1 and S1).

[0087] In step S116 next to step S115, the control apparatus MCidentifies the target alignment mark P1 from the plurality of alignmentmarks on the basis of the calculation result in step S115 and theinformation shown in Table 1 (information loaded to the controlapparatus MC in advance).

[0088] In step S117 next to step S116, the control apparatus MCcalculates the moving amounts (shift amounts for fine measurement) dxand dy of the wafer W to move the target alignment mark P1 into thevisual field HF of the high-magnification sensor S2, as shown in FIG.8B.

[0089] In step S118, the control apparatus MC determines whether themoving amounts dx and dy calculated in step S117 fall within theallowable range. The allowable range means the range of positional shiftamounts in which the position of the target alignment mark P1 can bedetected using the high-magnification sensor S2 without moving the waferW.

[0090] If it is determined that the moving amounts dx and dy fall withinthe allowable range, the control apparatus MC advances the process tostep S124 to determine the position of the mark FX1 and the position ofthe mark FY1, which are calculated in steps S113 and S114, as the X- andY-direction positions of the target alignment mark FXY1 (P1). Then, theflow advances to step S103 (returns to the main routine).

[0091] If it is determined that the moving amounts dx and dy falloutside the allowable range, the control apparatus MC outputs a commandto the stage control apparatus STC in step S119 to cause it to finelymove the wafer stage STG (i.e., the wafer W) to correct the shiftamounts dx and dy. With this operation, of the plurality of alignmentmarks, the target alignment mark P1 enters the visual field of thehigh-magnification sensor S2.

[0092] Next, in steps S120 and S121, the control apparatus MC executes,preferably simultaneously, high-magnification image sensing of the markFX1 (FX) for measurement in the X direction and high-magnification imagesensing of the mark FY1 (FY) for measurement in the Y direction.

[0093] Next, in step S122 and S123, the control apparatus MC executesposition calculation of the mark FX and position calculation of the markFY in parallel. With this process, the X- and Y-direction positions ofthe target alignment mark FXY1 are accurately calculated (detected).

[0094] As described above, in this embodiment, the alignment scope SCthat is designed to simultaneously sense alignment marks at a high andlow magnifications is arranged. With the alignment scope SC, imagesensing operations at high and low magnifications are preferablysimultaneously executed while keeping the wafer W stopped. The positionof an alignment mark (it is unknown whether the alignment mark is thetarget alignment mark) on the basis of the image sensing result at thehigh magnification. In addition, the target alignment mark isidentified, and its position (and positional shift amount) is detectedon the basis of the image sensing result at the low magnification.

[0095] It is determined on the basis of the position of the targetalignment mark whether the alignment mark whose position is detected atthe high magnification is the target alignment mark. If the alignmentmark whose position is detected at the high magnification is the targetalignment mark, the position detection result at the high magnificationis used as the position detection result of the target alignment mark.Otherwise, the wafer W is moved to a position at which the identifiedtarget alignment mark can be observed at the high magnification, and theposition of the target alignment mark is detected at the highmagnification.

[0096] If the target alignment mark is within the visual field HF of thehigh-magnification sensor S2 from the beginning, and the position of thetarget alignment mark is detected from the beginning, the position ofthe target alignment mark can be detected by one position detectionoperation. Hence, according to this embodiment, the speed of globalalignment can be increased.

[0097] Referring back to FIG. 6, after the position of the alignmentmark FXY1 is calculated in step S102, the control apparatus MC outputs acommand to the stage control apparatus STC to cause it to move the waferstage STG such that the alignment mark FXY2 shown in FIG. 4 enters thevisual field of the alignment scope SC. The control apparatus MCexecutes the same process as in step S102 (FIG. 7) for the alignmentmark FXY2, thereby calculating the X- and Y-direction positions of thealignment mark FXY2.

[0098] When the positions of the two alignment marks FXY1 and FXY2 aredetected, the position of the wafer W on the chuck CH can roughly beobtained. In this embodiment, target positions to be used to move theremaining alignment marks FXY3 (FX3 and FY3) and FXY4 (FX4 and FY4) intothe visual field HF of the high-magnification sensor S2 are calculatedon the basis of the position detection results of the alignments marksFXY1 and FXY2.

[0099] The target positions of the alignment marks FXY3 (FX3 and FY3)and FXY4 (FX4 and FY4) can be calculated in the following way. First, anX-direction shift amount (ShiftX), Y-direction shift amount (ShiftY),rotation component θ, and wafer magnification component Mag are obtainedon the basis of the X- and Y-direction positions of the two alignmentsmarks FXY1 and FXY2. The amounts ShiftX, ShiftY, and θ are shift amountswhen the wafer W is placed on the chuck CH, and correspond to the offsetof mechanical alignment. The amount Mag is the extension amount of theshot pattern on the wafer W.

[0100] If these amounts are large, even when the third and fourthalignment marks FXY3 and FXY4 are moved to the position immediatelyunder the alignment scope SC on the basis of their deigned positions,they cannot enter the visual field of the high-magnification system (M1,M2, and S2) of the alignment scope SC.

[0101] To prevent this, the shift between the shot layout of the waferand the stage coordinate system is calculated on the basis of theamounts θ, Mag, ShiftX, and ShiftY. More specifically, a smallcorrection amount to be used to align the grid on the wafer W to thegrid of the wafer stage STG is obtained. When the target positions ofthe alignment marks FXY3 (FX3 and FY3) and FXY4 (FX4 and FY4) arecorrected in accordance with the fine correction amount, the alignmentmarks FXY3 (FX3 and FY3) and FXY4 (FX4 and FY4) can be moved into thevisual field HF of the high-magnification sensor S2 without using thelow-magnification sensor S1.

[0102] When the θ component is corrected (for example, the wafer W isrotated by the chuck CH or stage STG), the third and fourth alignmentmarks FXY3 and FXY4 can be observed without any shift of the θcomponent. In this case, however, since rotation operation is necessary,the total process time becomes long. From the viewpoint of process time,it is advantageous to omit correction of the θ component.

[0103] In step S106 next to step S105, the control apparatus MC movesthe alignment mark FXY3 (FX3 and FY3) to the position immediately underthe alignment scope SC in accordance with the corrected target positionand detects the position of the alignment mark FXY3 using thehigh-magnification sensor S2. In step S107, the control apparatus MCmoves the alignment mark FXY4 (FX4 and FY4) to the position immediatelyunder the alignment scope SC in accordance with the corrected targetposition and detects the position of the alignment mark FXY4 using thehigh-magnification sensor S2. Thus, the global alignment is ended.

[0104] The arrangement example shown in FIG. 1 indicates a lithographysystem or exposure apparatus of off-axis alignment scheme. However, whenalignment marks can be simultaneously observed as low and highmagnifications, any other alignment scheme can be employed. Morespecifically, the present invention can also be applied to, e.g., a TTLalignment scheme for observing an alignment mark through a projectingoptical system LENS or a TTR alignment scheme for observing an alignmentmark through a reticle R.

[0105] The number of alignment marks to be detected in global alignmentand the number of alignment marks that can enter the visual field of thelow-magnification system are not particularly limited.

[0106] In addition, the method of identifying a target alignment markfrom a plurality of alignment marks in the visual field is preferablyapplied to the above lithography system or exposure apparatus capable ofsimultaneous observation with the low-magnification system andhigh-magnification system. However, the present invention can also beapplied to a type of system which observes an alignment mark with thehigh-magnification system on the basis of an observation result from thelow-magnification system. More specifically, the present invention canalso be applied to a sequential process for observing alignment marksusing the low-magnification system to identify and position-detect atarget alignment mark (S112, S115, and S116), calculating the shiftamounts dx and dy (S117), moving the stage STG by dx and dy (S119), anddetecting the position of the target alignment mark P1 using thehigh-magnification system (S120, S121, and S122).

[0107] In this case, since the sequential process is executed, the timerequired for global alignment becomes long. However, even in aconventional hardware configuration incapable of simultaneousmeasurement at low and high magnifications, a target alignment mark canbe identified from a plurality of alignment marks present in the visualfield.

[0108] Auxiliary patterns to be used to identify alignment marks are notlimited to the example shown in FIG. 2B. Any shape and layout can beemployed as long as alignment marks can be identified. For example, asshown in FIG. 2C, auxiliary patterns (identification marks) differentbetween alignment marks may be used. As shown in FIG. 2D, auxiliarypatterns (identification marks) IP may be laid out outside regions DAdefined for formation of alignment marks. In this case, when thepositions of a plurality of alignment marks that are present in thelow-magnification visual field are calculated, and then, the shape ofthe auxiliary pattern IP having a predetermined positional relationshipfrom the position (e.g., the central position) of each alignment mark isdetected by image processing such as template matching using a templatefor each auxiliary pattern, the target alignment mark can be identified.

[0109] Furthermore, as shown in FIG. 2E, in the alignment mark FXYformed from the X-direction measurement mark FX and Y-directionmeasurement mark FY, each alignment mark is made to partially have aform different from those of the remaining alignment marks and deformedwithout generating any influence, thereby identifying the alignmentmarks. In this case, the deformed portions (the projecting portions inthe example shown in FIG. 2E) correspond to auxiliary patterns. As anidentification method, various methods can be applied, including amethod of measuring the size such as the length of a correspondingportion.

[0110] [Second Embodiment]

[0111] Another embodiment which identifies a target alignment mark froma plurality of alignment marks in a single visual field will bedescribed. The basic hardware configuration, alignment marks, andmeasurement flow are the same as those of the first embodiment, and adescription thereof will be omitted. Only different points will bedescribed.

[0112] As shown in FIG. 3A, when a target alignment mark P1 is locatedoutside a visual field MF of a low-magnification sensor S1, positiondetection of the target alignment mark P1 is normally impossible.However, since alignment marks L1, M1, and N1 other than the targetalignment mark P1 is are present in the visual field MF, fine shiftamounts dx and dy or the position of the alignment mark P1 can becalculated in step S117 when the positional relationship between thealignment mark P1 and each of the alignment marks L1, M1, and N1 isknown.

[0113] For example, assume that the alignment mark L1 can be identifiedin accordance with its auxiliary pattern, and the position of thealignment mark L1 can be detected. In this case, the X- and Y-directionrelative distances between the alignment mark L1 and the targetalignment mark P1 are kx and ky. When the alignment mark L1 detectedwithin the visual field MF is shifted from a visual field center FC byshift amounts MX and MY, the amounts dx and dy of the movement of astage STG for fine measurement using the high-magnification system arecalculated by dx=MX+kx and dy=MY+ky, respectively.

[0114] As described above, even when the target alignment mark is notpresent in the visual field, or the target alignment mark cannot beidentified, as long as the alignment marks around the target alignmentmark can be identified, and their positions can be detected, theposition of the target mark can be calculated on the basis of the knownpositional relationship between each alignment mark and the target mark.Hence, the target mark can be moved to a visual field HF of thehigh-magnification system, and the position of the target mark can bedetected at a high magnification.

[0115] [Third Embodiment]

[0116] Still another embodiment which identifies a target alignment markfrom a plurality of alignment marks in a single visual field will bedescribed. The basic hardware configuration, alignment marks, andmeasurement flow are the same as those of the first embodiment, and adescription thereof will be omitted. Only different points will bedescribed.

[0117] Wafers are normally processed in blocks of lots. The lots areprocessed by a single manufacturing apparatus. When the reproducibilityof mechanical alignment is high, amounts ShiftX, ShiftY, and θcalculated for the first wafer are defined as the offset of mechanicalalignment. The position of the second wafer is shifted in advance by theamounts ShiftX, ShiftY, and θ. When this wafer is placed on a stage STG,the offset error of mechanical alignment becomes close to 0.

[0118] Hence, even when a plurality of alignment marks are observed in asingle visual field, the target alignment mark is sensed at the centerof the visual field. In this case, preferably, a search range SA inwhich an alignment mark is to be searched for in a visual field MF islimited near the center of the visual field MF so as not to search forany alignment mark outside the search range SA. The search range SA isset to be larger than a high-magnification visual field HF and alwaysallows observation of the target alignment mark within the allowablemechanical alignment error. With this arrangement, the time required forimage processing for searching for a target mark is shortened.

[0119] If the mechanical alignment accuracy and reproducibility arehigh, and the amounts ShiftX and ShiftY fall within the allowable rangefor detection at a high magnification, target alignment mark positiondetection using the low-magnification system and wafer movement on thebasis of the detected position of the target alignment mark can beomitted, as a matter of course.

[0120] [Fourth Embodiment]

[0121] Still another embodiment which identifies a target alignment markfrom alignment marks in a single visual field will be described. In thefirst to third embodiments, an auxiliary pattern is added to a targetalignment mark, and the target alignment mark is discriminated using theauxiliary pattern. The fourth embodiment provides a method ofdiscriminating a target alignment mark from a plurality of alignmentmarks present in a visual field without using any auxiliary pattern. Thebasic hardware configuration, alignment marks, and measurement flow arethe same as those of the first embodiment, and a description thereofwill be omitted. Only different points will be described.

[0122] In the example shown in FIG. 3C, a target alignment mark P1 and aplurality of alignment marks L1, M1, N1, and O1 are present in alow-magnification visual field MF. In the example shown in FIG. 3C, thepositions of the alignment marks are determined such that the alignmentmarks are separated from each other by different distances in the visualfield MF. More specifically, in the example shown in FIG. 3C, lengthsSPX1, SPX2, SPY1, and SPY2 are set to be different from each other.

[0123] For example, when the positions of two or more alignment markscan be detected in the visual field MF, the alignment marks can beidentified in step S116 on the basis of the relative positionalrelationship between the alignment marks. Then, the position (andnecessary moving amounts dx and dy) of the target alignment mark can bedetected in step S117 on the basis of the known positional relationshipbetween the target alignment mark and the identified alignment marks.

[0124] As described above, when the position of the target alignmentmark (e.g., P1) is detected, the moving amounts dx and dy necessary forobserving the target alignment mark at a high magnification can becalculated. By moving a stage STG in accordance with the moving amounts,the target alignment mark can be observed at a high magnification, andits position can be detected.

[0125] [Fifth Embodiment]

[0126] Still another embodiment which identifies a target mark from aplurality of alignment marks in a single visual field will be described.In the fifth embodiment, a method of identifying a target alignment markfrom a plurality of alignment marks that are present in a visual fieldwithout using any auxiliary pattern and setting different distancesbetween the plurality of alignment marks. The basic hardwareconfiguration, alignment marks, and measurement flow are the same asthose of the first embodiment, and a description thereof will beomitted. Only different points will be described.

[0127] In this embodiment, when all or some of alignment marks L1, M1,N1, O1, P1, and Q1 are present in a visual field MF, as shown in FIG.3D, the position of a target alignment mark is detected on the basis ofthe positions and number of alignment marks detected in the visual fieldMF. A description will be done below assuming that the target alignmentmark in the alignment marks L1, M1, N1, O1, P1, and Q1 is P1.

[0128] First, a case wherein all the alignment marks L1, M1, N1, O1, P1,and Q1, including the target alignment mark P1, are present in thevisual field MF, as shown in FIG. 3D, will be examined. In this case,the position of the target alignment mark P1 can be identified, and itsposition can be detected on the basis of the known position (the secondcolumn of the second row in this example) of the target alignment markP1 in the group of alignment marks L1, M1, N1, O1, P1, and Q1.

[0129] A method of estimating (determining) a target mark will bedescribed with reference to FIG. 3E, including a case wherein only someof the alignment marks are detected in the visual field MF. Adescription will be made assuming that the lower left apex of the visualfield MF is defined as the origin (0,0) of the coordinate system. Inthis case, the visual field MF corresponds to the upper right quadrantof the coordinate system.

[0130] Let Ax be the X-direction size of the visual field MF, Ay be theY-direction size, Mx be the X-direction interval between the alignmentmarks, and My be the Y-direction interval. Nx (number of columns) X Ny(number of rows) alignment marks are two-dimensionally laid out. Thefollowing conditions are satisfied.

Ax>Mx*(Nx−1)

Ay>My*(Ny−1)

[0131] The start alignment mark in the alignment mark grouptwo-dimensionally laid out is defined as the alignment mark at the lowerleft of the alignment mark group. The coordinates of the plurality ofalignment marks detected in the visual field MF are defined as (Xij,Yij){i=1, 2, . . . , k, j=1, 2, . . . , l, k≦Nx, l≦Ny}.

[0132] On the basis of the above definition, the method of determiningthe position (coordinates) of the target mark and the moving amounts(shift amounts) to the target mark will be described. As an example, amethod of identifying the target mark P1 on the basis of the number ofdetected alignment marks in the Y direction (the number of alignmentmarks whose positions can be detected in the visual field) will bedescribed.

[0133] When the number of alignment marks that can be detected in thevisual field MF is l (<Ny), the upper or lower portion of the Nyalignment marks arrayed in the Y direction falls outside the visualfield MF. When l=Ny, no alignment marks fall outside the visual field MFin the Y direction.

[0134] First, the moving direction (upward or downward) of the alignmentmark group in the visual field MF is determined. This determination canbe done in accordance with, e.g., the following procedure. First, anaverage position in the Y direction is obtained for each detectedalignment mark.${Meany} = {\frac{1}{k}{\sum\limits_{j = 1}^{k}y_{1y}}}$

[0135] Then, Meany is compared with the center of the visual field MFAyc=Ay/2. If Meany>Ayc, it is determined that the alignment mark grouphas moved upward in the visual field MF. If Meany<Ayc, it is determinedthat the alignment mark group has move downward in the visual field MF.

[0136] Next, the start coordinates of the alignment mark group arecalculated. The start coordinates are defined as the coordinates of thealignment mark at the lowermost position in the Y direction and leftmostposition in the X direction. When it is determined from the abovecomparison result that the alignment mark group has moved upward in thevisual field MF, a position Topy of the start alignment mark correspondsto an alignment mark position Miny=Min(y_(1j) {j=1, 2, . . . , l}) whichhas the minimum y-coordinate value in the detected alignment markpositions.

[0137] On the other hand, if it is determined that the alignment markgroup has moved downward in the visual field MF, the start alignmentmark may fall outside the visual field MF. An alignment markMaxy=Max(y_(1j) {j=1, 2, . . . , l}) which has the maximum y-coordinatevalue in the detected alignment mark positions corresponds to theposition of the alignment mark at the upper left corner of the alignmentmark group. Hence, a coordinate calculated by Maxy−My*(Ny−1) indicatesthe position of the start alignment mark. For the Y direction as well,the position of the start alignment mark is determined by the samecalculation as described above. With this operation, the coordinates ofthe start alignment mark at the lower left corner of the alignment markgroup can be determined.

[0138] That is, the coordinates of the start alignment mark can bedetermined in accordance with the following conditions.

[0139] If (Meanx≧Axc)

Topx=Min(x _(i1) {i=1, 2, . . . , k})

[0140] If (Meanx<Axc)

Topx=Max(x _(i1) {i=1, 2, . . . , k})−Mx*(Nx−1)

[0141] If (Meany≧Ayc)

Topy=Min(y _(1j) {j=1, 2, . . . , l})

[0142] If (Meany<Ayc)

Topy=Max(y _(1j) {j=1, 2, . . . , l})−My*(Ny−1)

[0143] Next, the target mark coordinates are estimated on the basis ofthe start alignment mark coordinates (Topx,Topy). The relative distances(Tdx and Tdy) between the target alignment mark and the start alignmentmark are known. Hence, the positions of the target alignment markcoordinates (Tx,Ty) are calculated by

Tx=Topx+Tdx

Ty=Topy+Tdy

[0144] Finally, the distance from the center of the visual field MF tothe target alignment mark is obtained, and the moving amounts (dx anddy) of the stage STG necessary for observing the center of the targetalignment mark at the center of a visual field HF of thehigh-magnification system are calculated in accordance with

dx=Ax/2−Tx

dy=Ay/2−Ty

[0145] Even in an extreme case wherein only one alignment mark isdetected in the visual field MF, the moving direction of the alignmentmark group can be determined, and the coordinates of the targetalignment mark that is not present in the visual field MF and thenecessary stage moving amounts can be determined. As a matter of course,even when the positions of all alignment marks are detected, thecoordinates of the target alignment mark and the necessary stage movingamounts can be determined in accordance with the above procedure.

[0146] The example shown in FIG. 3E will be described in detail. In theexample shown in FIG. 3E, Nx=2 and Ny=3. The group of six alignmentmarks has moved to the lower right side in the visual field MF. Thepositions of the alignment marks L1 and O1 can be detected. The targetalignment mark is P1. When the average values Meanx and Meany of thecoordinates of the detected alignment marks are compared with the visualfield center (Axc,Ayc), Meanx>Axc and Meany<Ayc.

[0147] Since Meanx>Axc, the minimum value Minx of the x-coordinate ofthe detected alignment mark is selected, and Topx=Minx.

[0148] In addition, since Meany<Ayc, the maximum value of they-coordinate of the detected alignment mark is selected, andTopy=Maxy−My*(3−1).

[0149] Since the distances Tdx and Tdy between the target alignment markP1 and the start alignment mark in the group of the six alignment marksare known, the coordinates (Tx,Ty) of the target alignment mark P1 canbe calculated in accordance with

Tx=Topx+Tdx

Ty=Topy+Tdy

[0150] Then, the moving distances necessary for moving the targetalignment mark P1 to the visual field center of the visual field MF (andvisual field HF) can be calculated by

dx=Ax/2−Tx

dy=Ay/2−Ty

[0151] In this way, even in a case wherein the target mark cannot bespecified in the visual field, when the total number of alignment marksand the relative position of the target alignment mark in the alignmentmark group are known on the basis of the positions and number ofdetected alignment marks, the position of the target mark can bedetected, and the moving amounts dx and dy necessary for moving thestage STG for detection at the high magnification can be calculated.When the stage STG is moved in accordance with the moving amounts, thetarget alignment mark can be moved into the visual field HF of thehigh-magnification system, and the position of the target alignment markcan be detected at the high magnification.

[0152] As described above, according to this embodiment, on the basis ofthe number and positions of alignment marks detected in the visual fieldMF (in consideration of the known relative position of the targetalignment mark in the group of alignment marks), in step S117, theposition of the target alignment mark can be detected, the movingamounts dx and dy necessary for observation of the target alignment markat a high magnification can be calculated, and by moving the stage STGin accordance with the moving amounts, the target alignment mark can beobserved at the high magnification, and its position can be detected.

[0153] [Sixth Embodiment]

[0154] An auxiliary pattern used to identify an alignment mark can beformed by transferring a pattern formed on a reticle R onto a wafer.This embodiment provides a method of transferring an auxiliary patternby means other than a reticle.

[0155] As shown in FIG. 2A, drawing alignment marks and auxiliarypatterns on the reticle R and exposing the alignment marks and auxiliarypatterns to a wafer in each step of semiconductor manufacturing restrictthe reticle design. Hence, it is preferable to transfer auxiliarypatterns onto a wafer using the function of an exposure apparatus. Inthis case, the marks or patterns to be drawn on the reticle R are onlyalignment marks (and device patterns).

[0156]FIG. 5A is a view showing the schematic arrangement of an exposureapparatus according to the sixth embodiment of the present invention.The same reference numerals as in FIG. 1 denote the same constituentelements. An alignment scope SC, processing apparatus P, illuminationlight source Li, and mechanical alignment apparatus MA are notillustrated in FIG. 5A for the illustrative convenience.

[0157] When global alignment is ended, the exposure apparatus executesstep-and-scan exposure or step-and-repeat exposure to transfer thepattern on the reticle R onto a wafer W. At this time, several alignmentmarks FXY are also simultaneously transferred. After that, the exposureapparatus executes a step of adding auxiliary patterns into thedefinition regions of the alignment marks or around them.

[0158] Patterns LM, MM, NM, and OM for auxiliary pattern formation areformed in advance, as shown in FIG. 5B, on a reference plate PL placedon the surface of the reticle R shown in FIG. 5A. When a masking bladeMS is driven, exposure light from an illumination system IL irradiatesonly a specific region of the reference plate PL. A reticle stage RSTGon which the reticle R and reference plate PL are placed is driven by alinear motor (not shown) such that a corresponding pattern on thereference plate PL moves into the exposure region while the position ofthe reticle stage is accurately measured by a position detectionapparatus (e.g., an interferometer). A wafer stage STG on which thewafer W is placed moves the wafer W such that the position on the waferW where an alignment mark is to be formed matches the exposure region bythe exposure light passing through the blade MS.

[0159] An example in which an alignment mark O1 shown in FIG. 2A and itsauxiliary pattern are to be formed will be described. First, inprojecting and exposing a device pattern, a pattern (this pattern isformed on the together with the device pattern) corresponding to thealignment mark O1 is transferred onto the wafer W together with thedevice pattern.

[0160] Next, the pattern OM on the reference plate PL, which is used toform an auxiliary pattern for identification of the alignment mark O1,is transferred to a predetermined position (in the definition region ofthe alignment mark O1 in this example) of the wafer W. At this time, theposition of the blade MS is controlled such that only the region OM ofthe reference plate PL is irradiated, as shown in FIG. 5C.

[0161] For auxiliary patterns for alignment marks L1, M1, N1, and P1 aswell, the mask patterns LM, MM, and NM are transferred every time thecorresponding device patterns and the alignment marks L1, M1, N1, and P1are transferred.

[0162] Alternatively, instead of preparing mask patterns for a pluralityof kinds of auxiliary patterns on the reference plate PL, only one maskpattern for an auxiliary pattern may be prepared and transferred topositions CPa, CPb, CPc, and CPd shown in FIG. 2B using the center ofthe alignment marks as a reference. To do this, for example, the bladeMS is located such that only the region of the mask pattern OM shown inFIG. 5B is illuminated, and the position of the wafer stage STG iscontrolled such that the mask pattern OM is transferred to the positionsCPa, CPb, CPc, and CPd.

[0163] The shape of the mask pattern for an auxiliary pattern is notlimited to that shown in FIG. 5B. For example, the mask pattern may bedesigned to transfer an auxiliary pattern having a rectangular shape,cross shape, or number sign shape as shown in FIGS. 2C and 2D byexample. Alternatively, for the mask pattern for an auxiliary pattern,part of an alignment mark may be extended, and the extended portion maybe used as an auxiliary pattern as shown in FIG. 2E by example.

[0164] The auxiliary pattern transfer operation can be controlled bysetting a job of the lithography system. Which type of auxiliary patternshould be transferred before, after, or at the time of exposure of analignment mark is set in the job. On the basis of this setting, thedriving positions of the blade MS and wafer stage STG can be controlledby a control apparatus MC.

[0165] [Device Manufacturing Method]

[0166] A device manufacturing method will be described below as anapplication example of the exposure apparatus according to the presentinvention described in accordance with the above embodiments by example.

[0167]FIG. 9 is a flow chart showing the entire flow of thesemiconductor device manufacturing process. In step 1 (circuit design),the circuit of a semiconductor device is designed. In step 2 (maskpreparation), a mask is prepared on the basis of the designed circuitpattern. On the other hand, in step 3 (wafer manufacture), a wafer ismanufactured using a material such as silicon.

[0168] In step 4 (wafer process) called a preprocess, an actual circuitis formed on the wafer by lithography using the above mask and wafer. Instep 5 (assembly) called a post-process, a semiconductor chip is formedfrom the wafer prepared in step 4. This step includes processes such asassembly (dicing and bonding) and packaging (chip encapsulation).

[0169] In step 6 (inspection), inspections including operation checktest and durability test of the semiconductor device manufactured instep 5 are performed. A semiconductor device is completed with theseprocesses and shipped (step 7).

[0170]FIG. 10 shows the detailed flow of the wafer process. In step 11(oxidation), the surface of the wafer is oxidized. In step 12 (CVD), aninsulating film is formed on the wafer surface. In step 13 (electrodeformation), an electrode is formed on the wafer by deposition. In step14 (ion implantation), ions are implanted into the wafer. In step 15(resist process), a photosensitive material is applied to the wafer.

[0171] In step 16 (exposure), the circuit pattern (device pattern) istransferred onto the wafer by the above exposure apparatus. At thistime, an alignment mark (position detection mark) and auxiliary patternare transferred to a position between chip regions or to a scribing linetogether with the circuit pattern. The auxiliary pattern may betransferred to the wafer using an auxiliary pattern mask prepared in theexposure apparatus.

[0172] In step 17 (development), the exposed wafer is developed. In step18 (etching), portions other than the developed resist image are etched.In step 19 (resist removal), any unnecessary resist remaining afteretching is removed. By repeating these steps, a multilayered structureof circuit patterns is formed on the wafer.

[0173] As described above, according to the preferred embodiments of thepresent invention, a target alignment mark can be identified from aplurality of alignment marks (position detection marks) and/or theposition of the target alignment mark can be detected. The targetalignment mark can be identified using, e.g., an auxiliary mark. Theauxiliary mark is preferably formed in a region where a mark or patternfor position detection can be formed, e.g., a region between chipregions. The auxiliary mark may be transferred to a wafer together witha device pattern and alignment mark by, e.g., projecting a master ontothe wafer. Alternatively, the auxiliary mark may be transferred to thewafer using a mask for the auxiliary pattern prepared in the exposureapparatus. According to the latter method, no auxiliary pattern need beformed when the master such as a mask or reticle is formed. Hence, therestriction at the time of master formation is reduced.

[0174] The target alignment mark can also be identified by separatingthe plurality of alignment marks by different distances and detectingthe distances between the alignment marks at the time of observation.Even in a case wherein the target mark is located outside the visualfield of an observation apparatus such as an alignment scope, when anyone of the plurality of alignment marks can be identified on the basisof the distance between the alignment marks, and the position of theidentified alignment mark can be detected, the position of the targetalignment mark whose position relative to the detected alignment markposition is known can be detected.

[0175] The target alignment mark can also be identified on the basis ofthe layout of the alignment marks to be observed. More specifically, theposition of the target alignment mark in the group is known. For thisreason, when the group can be observed, the target alignment mark can beidentified, and its position can be detected.

[0176] Alternatively, when the positions of alignment marks that arepresent in the visual field of the observation system are detected, theposition of the target alignment mark can be calculated on the basis ofthe number of the detected position detection marks and their detectionpositions in the visual field.

[0177] Such alignment mark identification methods can be applied notonly to global alignment but also to die-by-die alignment.

[0178] In addition, when alignment marks are observed using the high-and low-magnification systems simultaneously, and the observation resultby the low-magnification system indicates that the target alignment markis present in the visual field of the high-magnification system in anobservable state, the first position detection result by thehigh-magnification system is preferably employed. Otherwise, preferably,the wafer or high-magnification system is moved on the basis of theobservation result by the low-magnification system to move the targetalignment mark into the visual field of the high-magnification system,and the position of the target alignment mark is detected at a highaccuracy. Accordingly, alignment such as global alignment can beexecuted at a high speed, and a high throughput can be achieved.

[0179] According to the present invention, for example, a targetposition detection mark can be identified from a plurality of positiondetection marks, or the position of a target position detection mark ina plurality of position detection marks can be calculated.

[0180] As many apparently widely different embodiments of the presentinvention can be made without departing from the spirit and scopethereof, it is to be understood that the invention is not limited to thespecific embodiments thereof except as defined in the appended claims.

What is claimed is:
 1. An apparatus which detects a position of a markincluded in an object, comprising: a unit which senses an image of theobject, wherein a plurality of marks included in the object can beincluded in the image; a unit which extracts feature of a region, otherthan a region of a target mark of the plurality of marks, of the imagesensed by said sensing unit; and a unit which calculates a position ofthe target mark based on the feature extracted by said extracting unit.2. An apparatus according to claim 1, wherein the feature corresponds toan auxiliary mark, included in the object, associated with one of theplurality of marks.
 3. An apparatus according to claim 2, wherein theauxiliary mark is connected to one of the plurality of marks.
 4. Anapparatus according to claim 2, wherein the auxiliary mark is associatedwith the target mark.
 5. An apparatus according to claim 2, wherein theauxiliary mark is associated with one of the plurality of marks otherthan the target mark.
 6. An apparatus according to claim 1, wherein thefeature corresponds to relative positions of some of the plurality ofmarks.
 7. An apparatus according to claim 1, wherein the featurecorresponds to a position of one of the plurality of marks, of which aposition relative to the target mark is known.
 8. An apparatus accordingto claim 1, wherein the object is a substrate on which a device is to beformed.
 9. An apparatus according to claim 8, further comprising a stageunit which positions the substrate.
 10. An apparatus according to claim9, further comprising a unit which controls positioning of the substrateby said stage unit based on the position of the target mark calculatedby said calculating unit.
 11. An apparatus which exposes a substrate toradiant energy, comprising: a stage unit which positions the substrate;a unit which senses an image of the substrate, wherein a plurality ofmarks included in the substrate can be included in the image; a unitwhich extracts feature of a region, other than a region of a target markof the plurality of marks, of the image sensed by said sensing unit; aunit which calculates a position of the target mark based on the featureextracted by said extracting unit; and a unit which controls positioningof the substrate by said stage unit based on the position of the targetmark calculated by said calculating unit.
 12. An apparatus which exposesa substrate to radiant energy, comprising: a unit which projects apattern of radiant energy to the substrate; a unit which holds a maskhaving an auxiliary pattern, to be projected by said projecting unit,for identifying a target mark formed on the substrate; and a unit whichcontrols an operation of projecting the auxiliary pattern by saidprojecting unit.
 13. A substrate comprising: a region for a chip; and aplurality of marks formed such that a position of a target mark of theplurality of marks is recognized.
 14. A method of detecting a positionof a mark included in an object, comprising steps of: sensing an imageof the object, wherein a plurality of marks included in the object canbe included in the image; extracting feature of a region, other than aregion of a target mark of the plurality of marks, of the image sensedin said sensing step; and calculating a position of the target markbased on the feature extracted in said extracting step.
 15. A method ofmanufacturing a device, comprising steps of: sensing an image of asubstrate, wherein a plurality of marks included in the substrate can beincluded in the image; extracting feature of a region, other than aregion of a target mark of the plurality of marks, of the image sensedin said sensing step; calculating a position of the target mark based onthe feature extracted in said extracting step; and transferring apattern concerning the device to the substrate based on the position ofthe target mark calculated in said calculating step.